Reciprocating electric machine.



T. H. ALDRICH.

RBCIPROCATING ELECTRIC MACHINE.

APPLICATION FILED APR. 5. 1905.

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No. 814,259. PATENTBD MAR. 6, 1906.

T. H. ALDRICH.

REGIPROGATING ELECTRIC MACHINE.

APPLNMTIOH FILED APR. 5, 1905.

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UNITED STATES;

PATENT oFFIoE.

TRUMAN, HERBERT ALDRICH, BIRMINGHAM, ALABAMA.

RECIPROCATING ELECTRIC MACHINE.

- will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to reciprocating electric machines, and is intended for embodiment more particularl in motors, though it ma be equally applie to dynamos.

n its application tomotors the invention is particu arly adapted for emplo ment in connection with the o eration of rills, diggers, punchers, and ot erj tools requiring reciprocatory motion and reat power. The object is to provide a mac ine which may be utilized for such purposes that will have a high degree of efficiency.

I am aware that hitherto motors have been proposed in which the field-magnet consists of a cylindrical outer pole-piece and an inner axial pole-piece of op osite polarity, and the armature 1s mounte to slide on the inner ole-piece longitudinally of the annular space lietween the pole-pieces, reciprocation o the armature being produced by feeding the coil thereof with current that is periodically reversed. While for purposes of illustration I have shown a motor ofthis general type that is somewhat similar in that it-has a cylindrical pole-piece and an axial pole-piece of opposite polarity, combined with an armature reciprocable in the space between the two pole-pieces, I do not by any means limit myself to {a cylindrical form of motor or even to a completely-inclosed form. All that I consider of importance in this regard is that there be outer and inner pole-pieces of opposite polarity arranged parallel to each other,

with a longitudinally-reciprocable armature.

There are, however, essential differences between the present construction and the former types referred to. In these the armature conslsts simply of a coilof wire in which the periodically-reversed current through its influence on the magnetic flux produces reciprocation of the armature. With such a construction it is impossible to secure satisfactory efficiency, sincethere is such a large air-gap be tween the pole-pieces.

Specification of Letters Patent.

Application filed April 5, 1905. Serial No. 253,959.

. and resist the rupturing o Patented March 6, 1906 According to my invention the body of the armature is of suitable magnetic material, the

air-gaps being reduced to a minimum, and with this magnetic body is associated the ar mature-coil. Under these conditions the armature constitutes practically a traveling bridge for the lines of force passing between the pole-pieces. Moreover, while I do not limit myself tomounting the armature-coil on the armature-body, since it might be stationary with reference to the latter, yet when the coil is carried. by the magnetic body said body affords a superior path for the lines of force just where they will be most directly within the influence of the armature-current. It is true that it has been proposed previously to form the armature of a motor of this general description of a coil or coils of softiron wire; but aside from the fact that ironwound armatures have proved unsatis factoryit will be readily recognized that when the insulation around the individual'turns of wire and the spaces between these turns are taken into account an air-gap of such dimensions is-represented that the advantages obtained by my construction are quite lost. It is essential that the conductor of the armature shall be distinct from the magneticbody thereof. Thus in carrying my invention into effect I prefer to form the armature with a slotted body of magnetic material with acoil of non-magnetic material built up in the slot. or slots thereof, all air-gaps being as small as practicable. With such an armature it is possible to exert a tremendous pull.

In a motor such as I have proposed I find it of considerable importance that the magnetic field shall be evenly balanced. Otherwise as the armature reaches the strongest part of the field the lines of force from this region will tend to take the shortest path through the magnetic bod of the armature this path on the return movement of the armature. This balancing of the field maybe conveniently efiected by mounting an exciting coil or coils at each end of, the magnetic field, and in this 'wa a practically even field may be obtained.

11 the accompanying drawings I have illustrated diagrammatically certain embodiments of my invention. r

Figure 1. represents a vertical longitudinal section through a' motor constructedafter my invention, and Fig. 2 is a similar representation ofanother embodiment.

IIO

Referring more particularly to Fig. 1, A l represents the outer pole-piece, preferably, though not necessarily, in the form of a hollow cylinder, and B is the inner pole-piece, shown as an axial core rigid with the outer cylinder. The pole-pieces are'constructed of iron, steel, or other suitable magnetic material and are energized by field-coils C, located at o posite ends of the annular space between t e pole-pieces. These coils are so wound as to induce a polarity of one sign in the outer poleiece and a polarity of the opposite sign in t e inner member. To get the best results, the coils at the two ends should have the same number of turns and be arranged to balance the magnetic field. Howi ever, it is to be understood that the particular location and construction of the energizingcoils is not essential, and while I have shown the coils at the ends of the held outside of the path of the armature D they may be caused to overla the path of the armature, if desired. T e energizing-coils may be mounted. in any suitable manner to prevent accidental displacement. They are shown as carried in spools D of brass or other non-magnetic material, and should be securely anchored in place.

The armature I) comprises a body E of magnetic material slotted to receive the coil F. The air-gap between the magnetic body of the armature and the face of the outer poleiece is extremely small, and to prevent stickmg of the armature on the inner pole-piece,

' on which it slides, a sleeve G, of brass or any suitable non-magnetic material, is inserted between these two members. The armaturecoil is to be connected with the feeding-circuit in any suitable manner. One end of the coil may-terminate on the magnetic body E, in which case one of the feed-wires H may connect with the inner pole-piece, while the otherieed-wire connects with the other end of the coil, as desired. However, it will be understood that the particular manner of connecting the armature is an immaterial matter.

It will be readily understood that when current of constant direction is fed to the energising-coils in any suitable manner (not shown) and the armature is supplied with current that is periodically reversed the armature will have a reciprocating movement longitudinally in the space between the polepieces. The particular means for effecting the reversal of the armature-current isnot for the present of particular importance; but I have shown the reversal as being etlected b a pole-changer l, which is opera ted at suit al ile points in the cycle of movement by fingers J, mounted on a longitudinal rod K, carried by the armature outside of the outer pole piece. While I have referred to the armature as being the member supplied with the periodically-reversed current, it will be tools.

obvious without illustration that the fieldcoils instead may have the'direction of cur rent therein reversed.

In order to assist in the equalizing of the magnetic field, it may be considered advisable to provide means for neutralizing the slight increase in density toward the ends of the field. While this may be effected in a variety of ways-very simply by increasing the air-gap at these points-I consider that a collar of non-magnetic material inserted on one of the pole-faces at each end in advance of the energizing member at this point serves the pur ose excellently. I have illustrated such col are at K on the inner surface of the outer polepiece. For best results such col lars may be caused to increase in thickness, as shown, toward the fieldcoils.

In Fig. 2 I have shown a form of my invention particularly adapted to reciprocating The essential dilierence between this and the preceding form is that the armaturebody E is secured to the inner pole-piece B, which of course is now slidable in the outer polepiece A. With this construction the sleeve between the armature and the inner pole-piece is naturally omitted; but similar sleeves are inserted between the reciprocating pole-piece and the ends of the outer polepiece, in which it has its bearings. These sleeves are indicated at G. The form of motor illustrated in this view has the important advantage that the armature is prevented from canting and sticking, since the bearings are located so far apart. In a motor applied to a tool that is used for heavy work it is advisable to provide some cushioning means. I have made such provision by making the outer polepiece an inclosed cylinder, with the exception of vents L, located somewhat in advance of the extremes of movement of the armature. It will be obvious that as the armature advances from mid position toward one end the air will at first escape through the vent ahead until the armature passes this vent, when the air will be compressed. In order to increase the cushioning effect, packingqings M of non-magnetic material, or even of magnetic material, if sufficiently small, are letinto the periphery of the armature, and other packing rings N are secured to the spools of the field-coils, so as to bear against the reciprocating pole-piece. It will be noted that the vents serve not only for the cushioning effect, but also to provide ventilation for the interior of the motor. Even with some cushioning means provided there is considerable tendency for the armaturecoil of such a motor to become loosened,and in this figure I have illustrated one way in which the loosening may be avoided. According to this expedient the coil F consists of copper tape wound in the slot in the armature, each turn extending for the entire width of such slot. The tape is anchored in place by a disk 0, forming one side of the slot and bearing. forcibly against one side of the coil of tape, being suitably clamped, shrunk, or otherwise secured in position.

Another feature of great importance and value for motors used forthe kind of work indicated is shown in connection with Fig. 2. This feature is the provision of external means for automatically reversing the armature-current. The advanta e of this will be readily appreciated. In coa -di gers, for iristance, it frequently happens tat the tool becomes wedged in the material ated upon, and with the armature-current under the control of the armature itself, as shown in Fig. 1, the armature would be incapable of releasing itself. However, if a separate controller is provided'which will continue to reverse the current even when the armature is held against movement the armature will be caused to vibrate until it finally pulls the toolloose. I have shown this separate controller as being embodied in an auxiliary motor P, which operates the pole-changer. By means of resistance R the movement of the pole-changer may be tuned to the normal stroke of the main motor or the operation of the pole-changer may be varied to any degree desired. For instance, the armature-current may be reversed at such times that toward the end of the stroke of armature D the current will oppose the vmovement of the armature, thus aiding in the cushioning effect, besides using but a small amount of current. In this way not only the length but also the intensity of the stroke may be regulated. I consider this separate adjustable controller an improvement of great importance.

What IS claimed as new is 1. In a reciprocatin electric machine, the

combination with the eld having outer and inner pole-pieces of op osite polarity disposed parallel to each at er; of an armature reciprocable longitudinally in the space between the pole-pieces and comprising a body of magnetic material and a coil of conductor distinct from but associated with said body.

2. In reciprocating electric machine, the combin'a, ion with the field-magnet having inner and outer pole-pieces of op osite polarity disposed parallelto each otlier; of an armature reciprocable longitudinally in the space between the pole-pieces and comprising a body of magnetic material disposed in close magnetic relation to said po epieces' and a conductor distinct from but associated with said body.

3. In a reciprocating electric machine, the

combination with the field-magnet having inner and outerpole-pieces of, opposite polarity disposed parallel to each ot er; of an armature reciprocable longitudinally in the space between the pole-pieces and comprisbeing opep,

. inner ole-piece of opposite polarity ing a body .otmagnetic material disposed in close magnetic relation to said pole-pieces and a conductor distinct from but associated .with saidbody, and of a spacin member of non-magnetic material inserted etween said body and one of thepole-pieces.

4. In a reciprocating electric'machine, the combination with a field-magnet having outer and inner pole-pieces of opposite polarity arranged parallel to each other; of an armature reciprocable longitudinally in the space between said pole-pieces and consisting of a slotted core of magnetic material disposed in close magnetic relation to the polepieces and a conductor wound in said slotted body.

5. In a reciprocatin electric motor, the combination with a eld-magnet having outer and inner pole-pieces of opposite polarity arranged parallel to each other; of an armature reciprocable longitudinally in the space between said pole-pieces and consisting of a body of ma netic material disposed in close magneticre ation to the-pole-pieces and a conductor distinct from but associated with said body, and of means for automatically reversing the current in the conductor periodically during the cycle of movement.

6. In a reciprocating electric machine, the

combination with outer and inner pole-pieces, and with energizmg-coils arranged to create opposite polarities in the pole-pieces and to maintain the field balanced; of an armature reciprocable parallel to the pole -faces and comprisin a body of magnetic material disposed in c ose magnetic relationto the polepieces and a conductor associated with but distinct from said body.

7. In a reciprocating electricmachine, the

combination with inner andouter substan-' tially parallel .pole-pieces, and with energizing-coils located at opposite ends of the polepieces and arrangedto create opposite polarities in said pieces and to maintain the field balanced; of an armature reciprocable longitudinally in the space between the olepieces, and including a slotted magnetic ody disposed in close magnetic relation to the pole-pieces and a conductor wound in said slotted body.

8. In a reciprocating electric machine, the

combination with an outer pole-piece, and an inner ole-piece of opposite polarity reciprocable. lbngitudinally in the outer pole-piece;

consisting of a ody' of magnetic materialarranged contiguous the face of the outer pole-piece and a conductor associated With but distinct from said body.

9. In a reciprocating electric machine, the combination with an outer pole-piece, and an reel rocable ongitudinally 1n bearin sin t e en s of the outer pole-piece, and wit spacing memof an armature secured to said inner pole- E1608 tomove therewith and 

